Study On Fluctuation Characteristics And Its Restraining Technology Of High Speed Mlv

The electromagnetic high speed Maglev has many advantages such as non-contact, high speed, quick start-up, low energy expenditure and little environment influence. It has wide development and application foreground in railway transportation field. Supported by a national 863 project"Research of Vehicle's Electromagnetic Fields", this paper focuses on the research of high speed Maglev's fluctuation characteristic and its restraining technology. It provides powerful technical support for the research of domestic high speed Maglev. The main work and innovations of this paper are described as follows.Firstly, the electromagnetic force fluctuation characteristic of high speed Maglev is studied. Based on the basic theory of electromagnetic fields, the analytic model of electromagnetic force is established, in which the solving method of tangential force in AC electromotor's armature tooth wall is used for reference. Based on finite element analysis software ANSYS, the question of discontinuous medium in motion is solved using spatial discrete model. The distribution of the air-gap magnetic field as well as the changing and fluctuating rule of electromagnetic force is found. The error between analytical analysis and emulational analysis is within 10 percent, which achieves good mutual validation. Compared with previous model, the new analytic model has a distinct promotion. Moreover, the validity of the spatial discrete model is proved by another finite element analysis software MAXWELL.Secondly, the influence of the electromagnetic force'fluctuation on the dynamic performance of high speed Maglev is studied. For one thing, the fluctuation influence of electromagnetic force is studied using analytic method when the high speed Maglev is considered as a rigid body. The vehicle's nonlinear moving model is solved using both the curve composing method and equivalent approximation method. The vehicle's velocity and acceleration expressions under different moving state are constructed. The influence curves of the electromagnetic force's fluctuation to vehicle's velocity and acceleration are obtained. In addition, the frequency response is analyzed using finite element method when the high speed Maglev is considered as an elastomer. A 3D finite element model used for structural dynamics analysis is erected. The vehicle's amplitude to frequency response is gained when its stimulant signal is constructed according to the second chapter's analysis result. Through the analysis of frequency response, the influence of thrust ripple on vehicle's dynamic performance as well as resonant frequencies is found. It not only proves the harm of electromagnetic force'fluctuation but also provides theoretical basis for optimum moving control of the vehicle.Thirdly, the fluctuation restraining technology based on structural optimization is studied. The influential mechanism and specifically designed effect of the stator and rotor's different pitch are analyzed using fractional slot theory. An unequal rotor pitch design method is raised based on equivalent pole pairs. Giving attention to both fluctuation restraint and electricity generating, a programmed optimization design method of structure is proposed. The structure of levitated electromagnetic iron is optimized through minimizing the defined objective function. The result indicates that the thrust ripple decrease evidently. These structural optimization design methods not only reduce the fluctuation of electromagnetic force effectively, but also provide a method for high speed Maglev's structural optimization design.Fourthly, the fluctuation restraining technology based on the harmonic elimination of stator current is studied. The producing principle of harmonic magnetic field and its influence to the fluctuation of electromagnetic force are illustrated. The application methods of selective harmonic elimination technology in three-level inverter are analyzed. The limitation of selective harmonic elimination technology in three-level inverter is proved using mathematic method. The influence of inverter's switch angle error to harmonic elimination is analyzed. Combining with five-level inverter, a switch angle's selective method according to their robust coefficients is proposed. Calculation examples prove it reaches the prospective harmonic elimination result, which can reduce the fluctuation of electromagnetic force. This research provides reference for the design of inverter's control method.Fifthly, experimental research and fluctuation characteristic evaluation of high speed Maglev is implemented. An air-gap magnetic field measurement system of high speed Maglev is established and a soft measurement model is erected. A comprehensive measurement is implemented to the air-gap magnetic fields of magnetic levitation system built in magnetic levitation experimental center of NUDT. The measurement result validates the correctness of the analytic analysis and simulation. Combining with the dynamic performance evaluation items of high speed Maglev, Maglev's dynamic performance improved by the fluctuation restraint methods of electromagnetic force is analyzed. The research result of this paper indicates that high speed Maglev's fluctuation characteristic has been restrained effectively.